1. Field of the Invention
The present invention relates to an ink-jet recording apparatus including an eject recovery device of a recording head, which executes recording operations as ejecting liquid for recording, and relates to an eject recovery method.
2. Brief Description of the Related Art
An ink-jet printer, widely known as an image forming apparatus, is generally equipped with an eject recovery device for removing thickened ink, foreign particles and the like stuck to an eject port forming surface on its recording head so as to keep a stable ejecting performance of the ink-jet printer. The eject recovery device comprises one or a plurality of caps for covering an eject port forming surface of the recording head during non-printing operations to prevent ink as a liquid for recording from drying or evaporating, and a pump for sucking the thickened ink from and around the eject port forming surface via the cap.
Japanese published patent No. 03-61593 discloses a conventional ink-jet recording apparatus where an eject recovery operation is executed as a cap is being closely attached to the conventional recording head. A sucking ink operation described in this published patent is executed as follows: The cap is closely attached to an eject port surface of the recording head. A negative pressure is generated inside of the cap so that ink in the recording head is sucked via nozzles. Then ink remaining inside the cap is sucked as the inside of the cap is being communicated to the atmosphere. Finally the cap is detached from the recording head. Thus a series of recovery operations are executed.
The above-mentioned published patent discloses effects of preventing air from penetrating into nozzles and preventing ink from dripping/scattering from the cap, but does not imply anything about a xe2x80x9cmixed colorxe2x80x9d, a problem to be solved by the present invention.
The above-referred invention also proposes an absorbent arranged inside the cap, which attains effects of removing stagnant ink stuck around nozzles by sucking, and reducing remaining ink around eject port surface.
Ink-jet recording apparatuses employing color inks have been increasing, where a plurality of color inks are respectively ejected and a plurality of color ink dots are controlled in accordance with colors to be reproduced.
When a plurality of color ink tanks are mounted on the recording head equipped with a color cartridge where a plurality of nozzle rows for respective colors or a plurality nozzle groups for respective colors arranged on one nozzle row, usually caps for respective colors are not arranged, but one or the smaller number of caps than the color number to cover a plurality nozzle rows or nozzle groups are arranged so as to simplify a sucking mechanism and reduce a production cost of the apparatus.
When color printings are executed by the ink-jet recording apparatus, generally three colors Y, M and C (respectively mean yellow, magenta and cyan) and a black ink (Bk), namely 4 colors are employed. It is possible to print the black color by using three colors, Y, M and C, but usually the black ink is additionally employed so as to print a vivid black. When a first recording head to record in black ink and a second recording head to record in color inks are arranged in the ink-jet recording apparatus for this purpose, a first and a second caps for respective recording heads are required. Sometimes the first and second caps having the same capping mechanism are arranged respectively. Alternatively the first and second caps are constituted as a one-pieced member.
However, in conventional examples mentioned above, a plurality of inks mix each other and form a turbid ink which fills inside the cap, when the sucking operation is executed. Even after the cap is detached from the eject port forming surface of the recording head, the remaining turbid ink stuck to the eject port forming surface is mixed with ink inside nozzles. Which causes a problem of the so called xe2x80x9cmixed color phenomenonxe2x80x9d such that light colors such as yellow and the like are contaminated by the remaining turbid ink, when recording is performed on a recording medium. Since a pressure inside the ink tank is set always lower than that in nozzles, remaining mixed ink on the eject port surface of the recording head is sucked into the recording head via nozzles and finally is reversely flowed further inside the recording head.
As a trial to prevent the mixed color phenomenon, ink, not for recording, is ejected to remove the mixed ink in the nozzles. Japanese registered patent No. 2615619 discloses the ink ejection for preventing the mixed color phenomenon. The following procedure is described in the patent: ink is ejected for preventing mixing inks as a sucking pump is being driven, while the cap is detached from the recording head after the sucking operation.
To eject ink from nozzles during non-printing operations by driving the recording head, is sometimes referred as xe2x80x9cpre-ejectionxe2x80x9d. The pre-ejection is executed when removing thickened, stagnant bubbles and foreign particles in the nozzles to maintain ejecting stability, as well as when ejecting the mixed ink penetrated into the recording head.
However, when the cap is detached from the recording head after the sucking operation as ink is remaining in the cap, the following problem is remained unsolved. The predetermined amount of pre-ejection is not enough for ejecting mixed ink completely owing to ink properties and various conditions in water repellent status on the eject port surface of the recording head, consequently a fairly amount of ink must be wasted for the pre-ejection the following cases. (1) A large amount of ink is left at the recording head after detaching the cap from the recording head. (2) A large negative pressure (holding pressure) inside of the ink tank mounted on the recording head causes the more aggravated xe2x80x9cmixed color phenomenonxe2x80x9d due to a large amount of flowing mixed ink into nozzles.
In a sucking operation of a cap having a communicating valve to the atmosphere, when the communicating valve is opened to the atmosphere and cap is detached after ink inside the cap is removed after the sucking operation, a fairly large amount of ink must be pre-ejected for eliminating the mixed color completely, since the mixed ink in the nozzles diffuses further into the inside the recording head during a time between the sucking and detaching the cap.
The Japanese laid open patent No. 05-201029 discloses an arrangement having caps for respective colors, where inks are pre-ejected in the caps as being capped over the recording head by operating a piston pump, but it does not suggest anything about the mixed color.
The present invention is carried out in view of the above-mentioned situations to provide the ink-jet recording apparatus and the eject recovery method capable of eliminating a problem that a large amount of ink is wasted by the pre-ejection for preventing the mixed color phenomenon.
The present invention having the following constitutions solves the above-mentioned problems.
(1) An eject recovery method comprising steps of: a first step for performing suction from a first eject port for ejecting first ink and a second eject port for ejecting second ink different from the first ink through a cap for capping the first eject port and the second eject port while the cap is capping the first eject port and the second eject port collectively; and a second step for communicating an inside of the cap to atmosphere while the cap is capping the first eject port and the second eject port, and then performing suction from the cap while the inside of the cap communicating to atmosphere and while the cap is capping the first eject port and the second eject port, and concurrently ejecting ink into the cap from the first eject port and the second eject port.
(2) The eject recovery method according to (1), where the first ink and the second ink are different in colors.
(3) The eject recovery method according to (1), further comprising a third step for releasing the capping status by the cap after the second step.
(4) The eject recovery method according to (3), further comprising a fourth step for sucking from the cap as the capping status by the cap is being released after the third step.
(5) The eject recovery method according to (1), where the ink ejection into the cap starts after a predetermined time elapses after the sucking from the cap starts during the second step.
(6) An ink-jet recording apparatus comprising: a cap for capping a first eject port for ejecting first ink and a second eject port for ejecting second ink different from the first ink collectively, and equipped with a communicating valve to atmosphere; a sucking means for performing suction while the cap is capping the ink eject ports; and a control means for causing the sucking means to perform suction from the first eject port and the second eject port through the cap while the cap is capping the first eject port and the second eject port collectively, then causing the valve to communicate an inside of the cap to atmosphere while the cap is capping the first eject port and the second eject port, and thereafter causing the sucking means to perform suction from the cap while the inside of the cap communicates to atmosphere and while the cap is capping the first eject port and second eject port and concurrently ejecting ink into the cap from the first eject port and the second eject port.
(7) The ink-jet recording apparatus according to (6), where the first ink and the second ink are different in colors.
(8) The ink-jet recording apparatus according to (6), where the control means starts ejecting ink into the cap after a predetermined time elapses after the sucking from the cap starts.
(9) The ink-jet recording apparatus according to (6), where an absorbent is arranged inside the cap.
(10) The ink-jet recording apparatus according to (6), where electro-thermal converting bodies for generating thermal energy to be utilized to eject ink are arranged corresponding to the respective first eject port and second eject port.